The present invention relates to a method of manufacturing an array substrate for a display device and relates more particularly to a manufacturing method using divisional exposing method.
A flat display device such as a liquid crystal display device is light weight, thin, and consumes a low amount of electric power as compared with a display device such as a CRT (cathode ray tube). Because of such features, the flat display device has been recently employed in various kinds of devices such as a television display device, a computer display device, and a car navigation display device, which receives a signal from a satellite to detect a current position of the car and display the position of the car on the route to a particular destination.
Particularly, an active matrix type display device, which uses a switch element such as a thin film transistor (hereinafter called TFT) or an MIM (Metal Insulator Metal) element for each display pixel, can realize a good display image having no crosstalk between adjacent pixels. This type of the display device has been actively studied and developed.
The following will briefly explain the technique of the prior art, e.g., the liquid crystal display device of the active matrix type using thin film transistors as switch elements:
Specifically, the liquid crystal display device of the active matrix type includes an array substrate having a plurality of pixel electrodes arrayed, an opposite substrate having an opposite electrode formed, and a liquid crystal composition as an optical modulation layer sealed between both substrates. The array substrate is formed by the transparent insulating substrate such as glass and the pixel electrodes, which are connected to the TFTs, are disposed on the substrate in a matrix manner. Moreover, on the array substrate, scanning lines, signal lines, and storage capacitor lines for providing storage capacitors (Cs) are provided. The scanning lines are connected in common to the gate electrode of the TFTs arrayed in rows. The signal lines are connected in common to the drain electrode of the TFTs arrayed in columns. The storage capacitor lines are arranged to be opposite to the each pixel electrode so that an insulating layer may be formed between the each storage capacitor line and each corresponding pixel electrode.
In the array substrate of the active matrix type liquid crystal display, an insulating film, a conductive film or a dielectric film are formed. Then, resist coating, exposure, development, and patterning are repeated to manufacture the array substrate.
In the flat display device, e.g., a large size liquid crystal display device, having a high precision display image is required, and an exposure technique exhibiting high precision is needed to realize such a requirement.
For example, as shown in FIG. 9, there is known a divisional exposure method. In this method, the resist provided on the substrate is divided into a plurality of areas, and each area is exposed.
In the example of FIG. 9, an array substrate 100 including a display area at the center is divided into 18 areas, because of the limited size of the effective exposure area of each photomask, and each area is exposed. Display areas l1, l2, r1, r2, t1 to t4 and b1 to b4 of the array substrate shown by A of FIG. 9 correspond to non-display areas.
According to the above method, exposure with high precision can be realized. However, the respective layers of the array substrate must be repeatedly exposed sequentially by use of photomasks corresponding to A, l1, l2, r1, r2, t1 to t4, and b1 to b4. Due to this, and exposure must be performed eighteen times.
Such exposure is repeated for each respective layer. Since the number of the division areas is large, manufacturing time is increased.